The long range goal of this work is to obtain an understanding of the occurrence, location, binding, variety, changeability and functional role of the "water" present in human dental enamel in relation to various properties of human teeth. The primary enamel samples to be studied are sound enamel obtained from teeth removed for orthodontic reasons from persons near the two extremes of the human life span. The samples will be investigated by a variety of analytic techniques designed (1) to identify unambiguously and to assay the water in dental enamel, (2) to determine the location, state of binding and accessibility of the water in enamel, (3) to explain the irreversibility of the dehydration-hydration cycle of enamel, and (4) to determine if coupled substitutions, involving water, are related to the observed variations in the Ca/P molar ratios and heating-induced reduction of OH deficiencies in enamel.